With the recent spread of thermal heads, the demand for heat-sensitive recording materials is increasing rapidly. In prepaid cards, in particular, which show expeditious progress in the fields of communication, transportation, distribution, etc., many kinds of techniques for displaying magnetic information as visible information on the cards have come to be used. Such prepaid cards (magnetic cards) are being used extensively, and examples thereof include highway cards, prepaid cards for use in department stores, supermarkets, etc., and JR orange cards (railway cards).
However, since the area that can be used to display visible information is limited, large-amount prepaid cards often have a problem that renewed information concerning the balance becomes unable to add any more. Such cards are usually replaced with reissued cards and this has been disadvantageous in cost.
In order to overcome the above problem, there is a desire for a reversible recording material in which recording and erasion of information can be conducted repeatedly in the same area. Use of this material enables old information to erase and new information to display and, hence, avoids the necessity of issuing a new card as a substitution for an old card in which renewed information cannot be displayed any more. As such reversible recording materials which can record and erase information reversibly, heat-sensitive recording materials have been proposed which have a heat-sensitive layer comprising a resin matrix such as poly(vinyl chloride), a vinyl chloride-vinyl acetate copolymer, a polyester, or a polyamide, and an organic low molocular weight substance such as a higher alcohol or a higher fatty acid, dispersed in the matrix (e.g., JP-A-54-119377, JP-A-55-154198, and JP-A-2-1363). (The term "JP-A" as used herein means an "unexamined published Japanese patent application".)
Formation and erasion of an image in such recording materials utilize a reversible change in transparency of the heat-sensitive layer with changing temperature. Illustratively stated, such a recording material is in a transparent state in a temperature range of t.sub.1 -t.sub.1 ' (provided that t.sub.1 &lt;t.sub.1 ') and is in a milky and opaque state at temperatures of t.sub.1 ' or more. For heating the heat-sensitive recording layer, use of a thermal head is preferred particularly where the recording layer has been formed on a magnetic card. That is, recording is, for example, conducted by making the initial state of the recording layer transparent and selectively heating the recording layer with a thermal head to a temperature of t.sub.1 ' or more to allow the heated area to turn milky and opaque, thereby to record a character or design. Alternatively, recording may be conducted by making the initial state of the recording layer milky and opaque and selectively heating the recording layer with a thermal head to a temperature in the range of from t.sub.1 to t.sub.1 ' to allow the heated area to turn transparent. Erasion of the thus-recorded image is accomplished by heating the recording layer with a heated roll, thermal head, or the like to a temperature of from t.sub.1 to t.sub.1 ' in the case of the former recording technique and to a temperature of t.sub.1 ' or more in the case of the latter.
However, the above-described recording technique using a thermal head or other heating means has a problem that the reversible heat-sensitive recording layer suffers a change due to the heat and pressure applied, and when recording is conducted repeatedly in the same area of the recording layer, not only the recording layer is severely deformed to have an impaired appearance, but also the reversibility of the recording layer is impaired.